1. Field of the Invention
This invention relates generally to primers, and more particularly to an improved design of a bayonet type primer for tank ammunition.
2. Discussion of the Prior Art
Bayonet type primers have been used for many years in tank ammunition. Such tank ammunition comprises a 120 mm cartridge which includes a primer threaded into the base of a cartridge case and embedded into the propelling charge for the round contained within the case.
With the conventional primers, after the propelling charge has been ignited by the primer, the cartridge case base including the steel primer body is ejected into the confines of the fighting vehicle. In the case of the originally designed bayonet type primers, the ejected hot metal tube or body was able to come into contact with an ammunition round that was being held ready for loading after the chambered round was extracted. The ejected round could possibly land on the next round and start a fire within the close confines of the fighting vehicle.
In an attempt to solve this problem, the standard bayonet primers for the 120 mm tank ammunition were coated with silicone rubber (M129 primer) and silica filled rubber (SBR) (M125 primer) to keep them cool to the point that if a round came into contact with an ejected primer, the round would not be ignited. However, this coating is expensive and adds cost to the price of the ammunition round, and also, is subject to variations in processing. The rubber composition is generally formulated in batches and has a short shelf life.
In assembling the conventional bayonet primer to the ammunition round, the primer is threaded into the base of the cartridge case with the tubular portion being embedded into the propellant charge within the case. In some cases, due to the resistance of the propellant charge, it is not possible for the primer to be inserted all the way into the case on the first try whereupon it would be necessary to back out the primer and try to reinsert it. Not only was this operation time consuming, but in some cases the rubber coating would become damaged, rendering the primer unusable.
A typical bayonet type primer includes a primer head which houses the initial firing stage of the round. An ignition element, pressed into place in the confines of the primer head, is charged with a pyrotechnic composition that starts the firing train. The ignition element when activated disperses a flame through a retainer and sets off an explosive charge of black powder. The black powder charge in turn propagates through a closing plug which acts as a directional device to a third charge of Benite, which is comprised mainly of black powder and other pyrotechnic formulations, housed in the primer body. The third charge propagates through holes in the metal primer body initially sealed with a lacquer. This charge, propagating through the primer body, ignites the propelling charge contained in the ammunition case moving the ammunition projectile such as a penetrator out of the gun barrel and to its target.
With this type of arrangement, the process of making the primer according to conventional techniques requires a process step of applying a lacquer to seal the holes in the primer body to protect the pyrotechnic charge from moisture. This also adds to the cost of the round.